Conventional electron beam detectors measures the value of the current flow generated by the electron beam in order to measure high-intensity electron beams.
However, an electron beam detector employed in a scanning type electron microscope, for example, produces little electric charge when the intensity of the electron beam is relatively weak. Therefore, secondary electrons generated from the surface of a sample irradiated by an electron beam are collected and irradiated onto a fluorescent material. A photomultiplier tube is used to measure the fluorescence emitted by the fluorescent material.
Fluorescent materials well known in the art include CaF2, CaP5O14, P47, P46, YAG: Ce3+, YAP: Ce3+ (polycrystalline), and YAP: Ce3+ (single-crystal). However, a sufficient response has not been achieved with any of these fluorescent materials.